CBSE Set Qa1 Science Class X 1998 Sample Test Papers For Class 10th for students online

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Science Class X (CBSE)
You are on answers 1 to 20

General Instructions :
(i)   All questions are compulsary.
(ii) Question number 1 to 10 are very short answer question,carrying 1 mark each.They are to be answered in one or two sentences.
(iii) Question number 11 to 20 are short answer questions,each carrying 2 marks. Answer to them should not exceed 40 words each.
(iv)  Question numbers 21 to 30 are also short answer questions,each carrying 3 marks. Answer to them should not exceed 60 words each.
(v) Question numbers 31 to 33 are long answer questions,each carrying 5 marks. Answer to them should not normally exceed 100 words each.

Q1. Name the device which directly converts solar energy into electrical energy.
Ans1.
Solar cell.

Q2. Name the technique of collecting information through a satellite about an object from a distance.
Ans2. Remote sensing

Q3. An engine supplies 12,000 Jourles of energy per minute.How much power is supplied by it?
Ans3.
Energy = 12,000 J
Times = 1 minute = 60 s

Energy
Power = watt
Time

12,000
=
60
= 200 watt Power supplied is 200 watt


Q4. Lights from two different sources A and B have wavelengths 0.3 micron and 0.7 micron respectively.Which one of two lights carries more energy per photon?
Ans4
. Energy per photon is E = hn = h c/l
1
or, E a
l
Since lA < lB,

therefore, EB < EA Energy per photon is more in light A

Q5. Name any two gases whose presence in air causes green-house effect.
Ans5.
Carbondioxide and methane

Q6. Name the main constituents of common brass.
Ans6.
Copper and zinc

Q7. Which property of diamond gives it its special shine?
Ans7.
Diamond is transparent, has a high refractive index, and posseses excellent cleavage along many planes which can be polished. These properties give the diamond an extraordinary shine.

Q8. Boiled milk does not spoil quickly. Why?
Ans8.
Boiled milk does not spoil quickly because the spoilage causing bacteria and other micro- organisms get destroyed when the milk is boiled.

Q9. Which one of the following in a food chain will have maximum concentration of harmful chemicals in its body: small fish, Zooplankton, Birds, Phytoplankton.
Ans9.
Birds will have the maximum concentration of harmful chemicals because they are on the top of the given food-chain:

PhytoplanktonZooplanktonSmall fishBird

Q10. A farmer grows rice crop year after year in his field. He notices a gradual decrease in yield. What could be its cause?
Ans10.
The yield decreases gradually over the years because the monoculture of rice crop depletes the soil of the necessary mineral nutrients, especially nitrogenous nutrients.

Q11. Name the fuel gases formed when (i) steam, and (ii) a restricted amount of air are passed through a bed of red hot coke. Write the names of their combustible components.
Ans11.
(i) water gas, a mixture of CO and H2



Both the gases CO and H2 are combustible.
(ii) producer gas, a mixture of CO and N2


CO is the combustible component in the producer gas.

Q12. Calculate the power of an engine which can lift 300 Kg of water through a vertical height of 15m in 15 second. (g = 10 m/s2)
Ans12.
mass = 300 kg
height = 15 m
g = 10 m/s2
Work done by the engine = 300 x 15 x 10 = 45,000 J
time = 15 s
45,000
Power = 3,000 W
15
The power of the engine is 3 kW

Q13. Mention any two differences between chemical and nuclear reaction.
Ans13.

Chemical reaction

Nuclear reaction

1.Only the outermost (valence) electrons of the atom participate in a chemical reaction
hence no new elements are formed

2.Energy released or absorbed is small

1.The composition of the nucleus undergoes
a change and hence new nuclei or particles
form

2.Energy released is extremely large

Q14. Kerosene burns in a cooking stove to give a blue flame while it gives a yellow flame when burnt in a lantern. Give reasons for this difference.
Ans14.
A flame is blue when the supply of oxygen is adequate for the fuel to burn completely.The flame becomes yellow when the supply of oxygen is inadequate and the fuel does not burn completely. In the cooking stoves the construction is such that the supply of sufficient air is ensured and the
fuel burns completely. Whereas, in the lanterns the wick does not provide for the complete burning of the fuel and the flame becomes yellow and sooty.

Q15. Give two differences between a star and a shooting star.
Ans15.

Star

Shooting Star

1.It is made up of gases like hydrogen, helium.

2. It has light of its own

1. It is made up of rocks & metals

2. It has no light of its own but is seen as a bright streak of light when it burns due to fictional heat produced on entering the earth's atmosphere.

Q16. What is smog? Name any two diseases caused by smog.
Ans16.
Smog is a combination of smoke and fog. Smoke is made up of tiny particles of carbon, ash, oil, etc. Fog is made up of water droplets suspened in the air. Smog does not rise up and stays close to the earth's surface.
Two of the diseases which are caused by smog are:
1. Irritation to the eyes, nose and throat;
2. Asthma and other respiratory disorders.

Q17. A trivalent metal X is manufactured by the process of electrolysis. It is the most abundant metal in the earth's crust. Identify the metal and state its two uses.
Ans17.
The metal should be aluminium because Aluminium is the most abundant metal in the earth crust and the third most abundant element in nature. Aluminium is trivalent (Al3+) and is prepared by electrolytic refining. Aluminium is used for:
1. Preparing electricity conducting wires, and
2. Preparation of light weight alloys for aircrafts etc.

Q18. What is meant by a functional group in an organic compound? Give the structural formulae of the functional groups in (i) Acetic acid and (ii) Ethyl alcohol.
Ans18.
Functional group in an organic compound is a group of element which replaces -H from the hydrocarbons and imparts the group specific properties. For example, -OH is the hydroxyl group which replaces -H from H-CH3 and produces properties so characteristic of alcohols. Structural formulae of the functional groups in:

Acetic acid (CH3-COOH )

Ethyl Alcohol (CH3-OH)

-O-H

Q19. What is sickle cell anaemia? What is its direct effect?
Ans19.
Sickle cell anaemia is found in persons whose red blood cells contain a deffective type of haemoglobin having the appearance of a sickle. The direct effect of this trait is that the oxygen carrying capacity of the blood gets decreased.

Q20. Mention the difference between the food habits of organism belong to the first and third trophic levels. Give one example of each of them.
Ans20.
The first trophic level is the level of producers. Green plants are the producers and generate their food on their own.They have chlorophyll with which they trap solar radiations and convert it into the chemical bond energy.
The third trophic level is the level of carnivores. They prey on the herbivores.

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